Transient Flow in Discretely Fractured Porous Media

This paper presents a semianalytical model for transient flow into multiple vertical wells producing from a porous medium containing randomly distributed discrete fractures. Both vertical openhole wells and hydraulically fractured vertical wells are considered. The semianalytical model simulates pressure and pressure-derivative characteristics of wells and flow distribution along and through both the natural and the hydraulic fractures. The study shows that single or multiple isolated natural fractures yield negative pseudoskin factors in vertical wells near isolated fractures. The negative pseudoskin factor is a function of fracture conductivity, density, length, distance from the wellbore, and azimuth. Using the model, we demonstrate that the shape of the pressure derivative is related to fracture distribution. The results of this study indicate that the conventional double-porosity analysis to predict the storativity ratio of a naturally fractured system is not reliable. Also, the displacement between two semilog straight lines is not necessarily a good indicator of the storativity ratio.